Blushing (Milkiness) is a milky grey cloud appears on the surface of the paint film.
Common Cause
Blushing can occur when spraying in high humidity levels, air from the spray gun and solvent evaporation lowers the substrate temperature below the dew point causing moisture in the air to condense in or on the paint film. The condition is aggravated when:
(1) Too fast drying or poor quality thinner is used.
(2) Fanning dry the paint film to speed up the solvent release.
(3) Inadequate heating and or air movement
Prevention
Use the correct, good quality thinner
Add the recommended amount of retarder when spraying in humid conditions
Use the proper gun set up and techniques
Ensure the paint booth is properly ventilated and heated adequately
Repair
Should blushing occur during application apply heat to the affected area or add retarder and apply additional coats. If the finish has dried, minor blushing may be corrected by compounding or polishing.
Severe cases will require sanding and refinishing